HTML Code:
register_sidebar was called <strong>incorrectly</strong>. No <code>id</code> was set in the arguments array for the "Left Sidebar" sidebar. Defaulting to "sidebar-1". Manually set the <code>id</code> to "sidebar-1" to silence this notice and keep existing sidebar content. Please see <a href="https://codex.wordpress.org/Debugging_in_WordPress">Debugging in WordPress</a> for more information. (This message was added in version 4.2.0.) in /home/cornetsd/domains/cornetsdegroot.com/public_html/wp-includes/functions.php on line 4773
This is Atahualpa showing it's age. Wordpress is changing and Atahualpa isn't. Unfortunately there are fewer and fewer people using Atahualpa and donations have dried up (when was the last time you donated?) and there is no incentive to keep the theme up to date.
If you set wp_debug to 'false' in your wp_config.php file, those messages should go away.
as for the issue you have, did you clear your browser cache after disabling all your plugins? A google seaarch seems to indicate that the code may come from a contact form/google map